[efficax]

This sort of question comes up a lot when people are talking about big social media sites and there are two answers, both related to scale. First is that things really do just go more slowly when you are larger. There are more stakeholders and greater consequences to change. You don't change anything without measuring it first through flagging and limited a/b releases, and often those a/b tests actually fail to show a reason to release the change since the stats show that even though you think it's an improvement, it actually has a negative impact on key metrics.

But the second one is that while the site might seem simple and straightforward, the way it has to be engineered to handle the massive scale of a Reddit (with over a billion active monthly users) makes it very, very complicated internally. I'm not familiar with Reddit specifically but having seen the architecture at other places of similar size, I can tell you there's a ton going on behind the scenes to make it possible to reliably serve that many users and that makes major changes very complicated, involving multiple teams, and lots of planning.